Response to detection of an overcharge event in a series connected battery element

ABSTRACT

A system and method for identifying and responding to exceptional charge events of series-connected energy storage elements can include: a first charge imbalance detection system monitoring, using the microprocessor, the energy storage system for a charge imbalance using a first detection modality, said first charge imbalance detection system initiating a reduction of said charge imbalance using a first response modality; a second charge imbalance detection system monitoring, using the microprocessor, the energy storage system for an exceptional charge event of a particular one battery element of the plurality of battery elements using a second detection modality different from said first detection modality; and a remediation system initiating a response to said exceptional charge event using a second response modality different from said first response modality, said response decreasing a risk associated with said exceptional charge event.

FIELD OF THE INVENTION

The present invention relates generally to chargeable battery packs, andmore specifically, but not exclusively, to detection and remediation ofan exceptional charge state of a series element of a chargeable batterypacks.

BACKGROUND OF THE INVENTION

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also be inventions.

Battery packs, for purposes of this disclosure, are series-connectedbattery elements. These elements may, in turn, include a parallel,series, or combination of both, collection of chargeable energy storagecells, usually rechargeable cells. Collectively all these cells storeenergy for the battery pack. The series-connected battery elements may,in turn be subdivided into collections of modules, each module includingone or more series-connected battery element.

In many instances, the battery pack may be treated as a monolithic unit,providing energy for operation. However, to enable such treatment,individual cells, series-elements, and modules are processed in order toachieve a desired average monolithic effect. One particular concern isthat at the individual level, the series elements are not the same andstore differing amounts of energy and charge/discharge at differentrates. These variations are natural and expected. In certain situations,the variations can lead to an exceptional variation, defined herein asan exceptional charge state, in which an individual series element isexcessively overcharged or overdischarged (as compared to somethreshold).

Overcharge of a lithium-ion battery can lead to thermal runaway, eitherdirectly or via increased susceptibility to abuse due to decreasedchemical stability. When charging a battery pack which includes morethan one series element, an initial imbalance in the state of charge ofthe series elements can result in overcharge of one or more of theseries elements, even when the voltage of the battery pack does notindicate overcharge. There are conventional solutions to mitigate thispotential hazard that monitor series element voltages and are in placeto ensure balance prior to charging. However, due to the potentialseverity of exceptional charge events, particularly for overchargeevents, additional systems for identifying series element overcharge ina battery pack before the event becomes severe are desired in the eventthat the voltage monitoring and balancing system malfunctions or mayotherwise insufficiently address the exceptional charge event.

What is needed is a system and method for identifying exceptional chargeevents of series-connected energy storage elements, and respondingappropriately to detected exceptional charge events.

BRIEF SUMMARY OF THE INVENTION

Disclosed is a system and method for identifying and responding toexceptional charge events of series-connected energy storage elements.The following summary of the invention is provided to facilitate anunderstanding of some of technical features related to detecting toexceptional charge events of series-connected elements and responsesthereto, and is not intended to be a full description of the presentinvention. A full appreciation of the various aspects of the inventioncan be gained by taking the entire specification, claims, drawings, andabstract as a whole. The present invention is applicable to otherimplementations in addition to electric vehicles such as stored energycases providing energy time shifting of renewable energy generation(e.g., solar and wind generators), to other arrangements ofseries-connected energy storage elements, and may be applied to othercell chemistries.

A microprocessor-implemented response system for an exceptional chargeevent in an energy storage system having a plurality of series-connectedbattery elements, including a first charge imbalance detection systemmonitoring, using the microprocessor, the energy storage system for acharge imbalance using a first detection modality, the first chargeimbalance detection system initiating a reduction of the chargeimbalance using a first response modality; a second charge imbalancedetection system monitoring, using the microprocessor, the energystorage system for an exceptional charge event of a particular onebattery element of the plurality of battery elements using a seconddetection modality different from the first detection modality; and aremediation system initiating a response to the exceptional charge eventusing a second response modality different from the first responsemodality, the response decreasing a risk associated with the exceptionalcharge event.

A computer-implemented method to respond to an exceptional charge eventin an energy storage system having a plurality of series-connectedbattery elements, including monitoring, using the microprocessor, theenergy storage system for a charge imbalance using a first detectionmodality; initiating a reduction of the charge imbalance using a firstresponse modality; monitoring, using the microprocessor, the energystorage system for an exceptional charge event of a particular onebattery element of the plurality of battery elements using a seconddetection modality different from the first detection modality; andinitiating a response to the exceptional charge event using a secondresponse modality different from the first response modality, theresponse decreasing a risk associated with the exceptional charge event.

Any of the embodiments described herein may be used alone or togetherwith one another in any combination. Inventions encompassed within thisspecification may also include embodiments that are only partiallymentioned or alluded to or are not mentioned or alluded to at all inthis brief summary or in the abstract. Although various embodiments ofthe invention may have been motivated by various deficiencies with theprior art, which may be discussed or alluded to in one or more places inthe specification, the embodiments of the invention do not necessarilyaddress any of these deficiencies. In other words, different embodimentsof the invention may address different deficiencies that may bediscussed in the specification. Some embodiments may only partiallyaddress some deficiencies or just one deficiency that may be discussedin the specification, and some embodiments may not address any of thesedeficiencies.

Other features, benefits, and advantages of the present invention willbe apparent upon a review of the present disclosure, including thespecification, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present invention and, together with the detaileddescription of the invention, serve to explain the principles of thepresent invention.

FIG. 1 illustrates an energy storage system;

FIG. 2 illustrates a chart of loaded voltage versus State-of-Chargecurve for a single representative series element;

FIG. 3 illustrates a chart of a derivative of the curve of FIG. 2;

FIG. 4 illustrates a graph of a set of series element voltages duringcharging;

FIG. 5 illustrates a system including exceptional charge event detectionand response;

FIG. 6 illustrates a flowchart for a detection process;

FIG. 7 illustrates a graph of a transient discharge event for a set ofseries battery elements; and

FIG. 8 illustrates a graph of a transient charge event for a set ofseries battery elements.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide a system and method foridentifying exceptional charge events of series-connected energy storageelements. The following description is presented to enable one ofordinary skill in the art to make and use the invention and is providedin the context of a patent application and its requirements.

Various modifications to the preferred embodiment and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiment shown but is to be accorded the widestscope consistent with the principles and features described herein.

It is important that a rechargeable energy storage system havingmultiple series-connected energy storage element, particularly for thosestoring high energy levels and/or charging at high energy transferrates, to detect exceptional charge events, more particularly inidentified individual series elements. The following disclosure includesdetection of exceptional charge events and possible responses todetected exceptional charge events. The detection addresses detection intwo different types of cases: a “steady state” case and a “transient”case. Steady state is characterized as those scenarios where energychange events tend to be predictable, consistent, longer time scales(several minutes, to hours, to longer periods), and relatively lowerenergy and “transient” cases tend to be on an opposite side of thisspectrum: unpredictable, variable, shorter time scales (˜1 second toseveral minutes), and relatively higher energy. There are not brightlines categorizing these cases. There are two representative uses thathighlight these cases: 1) an electric vehicle (EV) case and 2) astationary storage case. In the EV case, external charging isrepresentative of the steady state case. In the stationary storage case,withdrawal or external grid charging of stored energy is representativeof the steady state case. For the EV, internal regenerative events arerepresentative of the transient case, as well as energy use thatresponds to the user's driving pattern and traffic/road conditions. Forthe stationary storage case, charging from a wind or solar generator isrepresentative of the transient case.

Whether categorized as transient or steady state operation, duringcharging a system advantageously monitors for and is able to detect anexceptional charge event as an overcharge event. In contrast, duringdischarge the system monitors for and is able to detect any exceptionalcharge event as an overdischarge event. Different information andmethods are used for the detection based upon which type of case.Broadly speaking, detection takes advantage of anything that affectsloaded voltage vs. SOC. The system and methods of the preferredembodiments detect differences between an actual SOC and a measured SOCas energy storage in one or more battery cells changes (e.g., duringcharging and discharging). The preferred embodiments are able to takeadvantage of anything measurably different between battery cells thatarise because of SOC differences.

Responding to a detected exceptional charge event does not depend uponthe use, but on the nature of the exceptional charge event. That is, anappropriate response will depend upon whether the detected exceptionalcharge event is an overcharge event or an overdischarge event.

For purposes of this application, “transient” means a period of aboutone second, a few minutes, or a shorter period. For purposes of thisapplication, “steady state” means a period of several minutes, severalhours, or longer period.

This application is one of four related applications that addressvarious aspects of the detection and response to exceptional chargeevents. In addition to this application, those other three applicationsare: U.S. patent application Ser. No. 13/689,787 entitled “TRANSIENTDETECTION OF AN EXCEPTIONAL CHARGE EVENT IN A SERIES CONNECTED BATTERYELEMENT” and filed concurrently herewith, U.S. patent application Ser.No. 13/690,105 entitled “STEADY STATE DETECTION OF AN EXCEPTIONAL CHARGEEVENT IN A SERIES CONNECTED BATTERY ELEMENT” and filed concurrentlyherewith, and U.S. patent application Ser. No. 13/690,341 entitled“RESPONSE TO DETECTION OF AN OVERDISCHARGE EVENT IN A SERIES CONNECTEDBATTERY ELEMENT” and filed concurrently herewith. All these applicationsare hereby expressly incorporated by reference thereto in theirentireties for all purposes.

FIG. 1 illustrates an energy storage system 100 (ESS). ESS 100 includesa set of battery elements 105 i, i=1 to N where N can be tens, tohundreds, to thousands of series-coupled elements. A battery element 105x in the present context includes individual battery cells, but alsoincludes aggregations of parallel and/or series connected elements thatare, in turn, connected in series with another battery element (e.g.,battery elements 105 x−1 and 105 x+1). The embodiment disclosed hereinis focused primarily on battery elements 105 with lithium-ion chemistrybut may be adapted to work with other cell chemistries.

A battery management system (BMS) 110 is electrically communicated tothe components of ESS 100 for monitoring, data acquisition, and control.As such it includes sensors and control elements (e.g., combinatorialand arithmetic logic elements and in some cases stored-programprocessing units executing instructions from a memory and the like) thatperform the functions and processes described herein.

Individual cells are packaged and there may be additional packaging ofcollections of the battery cells of each particular battery element 105i. Individual cells may be combined in desired parallel and seriesarrangements and packaged together into modules that may be furtherelectrically connected together. There are logical sets of elements(e.g., battery element 105) that each include a positive terminal and anegative terminal reflecting a relative voltage level. In general forthe series-connected battery element, a positive terminal of aparticular battery element 105 i is electrically communicated to anegative terminal of an “upstream” battery element 105 i−1. A negativeterminal of battery element 105 i is electrically communicated to a“downstream” battery element 105 i+1. This is done for i=1 to N numberof battery elements, with the positive terminal of battery element 105 ₁coupled to an ESS positive terminal 115 and the negative terminal ofbattery element 105 _(N) coupled to an ESS negative terminal 120.

A relative terminal voltage between ESS positive terminal 115 and ESSnegative terminal 120 provides the collective net contributions of the Nnumber of battery elements 105 _(N). ESS 100 is charged and dischargedthrough these terminals. ESS 100 stores energy for many differentapplications, including energy for an electric propulsion motor of anelectric vehicle (EV) and energy storage supporting time-shifted energyproduction from wind and solar generators and the like. While theterminal voltage presents a statistical effect of the aggregatedseries-connected battery elements 105, the voltages of the individualbattery elements 105 i vary between each other. There are two differenttypes of variations that are specifically mentioned here, though othervariations may also come into play, sometimes with lesser or greatercontribution. An individual battery element 105 i will have a voltageoffset variation and a voltage gain measurement error. (Note that thisis a measurement error, not an actual variation in the voltage of thebattery element. The voltage of the battery element will include naturalvariations, but this is due to normal charge/discharge cycling of theelement. The same charge/discharge cycle may not change SOC of twobattery elements identically.) BMS 110 includes a voltage measurementand balancing system (VMBS) 125 that acquires individual voltagemeasurements, including the individual voltages of battery elements 105.

It is the case that a voltage of ESS 100 could indicate a charge levelwithin design specification while an actual voltage level of a batteryelement 105 x could be different than other elements. When thedifference is excessive, the different voltage levels of the batteryelements produce a potentially dangerous charge imbalance. Without VMBS125, the charge imbalance could produce a potential hazard ofovercharging some battery elements 105 because a charger for ESS 100would see the terminal voltages as being within specification. Also,without VMBS 125, the charge imbalance could produce a potential hazardof overdischarging some battery elements 105 during energy withdrawalfrom ESS 100 which would be based on the “average” charge and anyundercharged cells could have too much energy withdrawn.

VMBS 125 mitigates this potential hazard by monitoring the individualvoltages of battery elements 105 and ensures balance and/ornon-hazardous charging prior to charging of ESS 100. As noted above, dueto potential severity of overcharge events, BMS 110 includes furtherstructures and processes for identification of series elementexceptional charge events in ESS 100 before such event(s) become severe.This can be considered a backup to VMBS 125 in case VMBS malfunctions orotherwise does not detect a particular condition of battery elements 105that could lead to dangerous imbalance.

VMBS 125 can malfunction in different ways, one of which is that it canexperience a measurement error. Without such a measurement error, VMBS125 could respond to an imbalance by asserting a status signal to BMS110 that results in some type of response. That response could includeinhibition of an initiation of charging of ESS 100, or termination ofcharging after it has begun. VMBS 125 with a measurement error couldcontribute to a dangerous imbalance by allowing charging tostart/continue or by improperly balancing voltage levels based uponincorrect measurement values, the improper balancing creating the veryovercharge or undercharge event to be protected against.

BMS 110 further includes an exceptional charge event detector 130 thatmonitors battery elements 105 during operation of ESS 100. One or moremeasurable parameters of battery elements are monitored and comparedagainst a reference to determine whether an exceptional charge event isoccurring, or has occurred. As discussed in more detail below, thereference may be determined from a statistical characterization of thecollection of battery elements over time, with a “sufficient” deviationof any measured value from the reference an indication of a possibleexceptional charge event, or a real-time characterization of relevantparameters from ESS 100.

FIG. 2 illustrates a chart of loaded voltage versus State of Charge(SOC) curve 200 for a single representative series element 105.Specifically in this case, battery element 105 includes eight parallelLithium-ion cylindrical format cells being charged in a steady-stateimplementation. (Other implementations and arrangements will likelyproduce a different absolute curve; however the effect will be similarto that shown.) SOC curve 200 provides the voltage of the batteryelement as it is charged to different SOC levels. SOC curve 200 iseffectively linear in the range of 10% to 100% SOC during “normal”charging.

FIG. 3 illustrates a chart of a derivative curve 300 of SOC curve 200 ofFIG. 2. Derivative curve 300 is a change of voltage per change of charge(dV/dQ) and confirms the linearity of SOC curve 200 in the normal chargerange. Above the normal range (e.g., greater than 100% SOC) whereovercharge begins, a slope of SOC curve 200 begins to become non-linear.Initially the slope increases and then it decreases, with the changesignificant. These changes in the slope are confirmed in derivativecurve 300 at charge levels greater than 100%.

Not shown in FIG. 2 and FIG. 3 is that portion of SOC curve 200 (andcorresponding portion of derivative curve 300) relating to overdischarge(charge levels below the “normal” range). Overdischarge in that portionof the charging range “below” the normal range will also experiencemarked changes in slope. The general concepts described herein withrespect to overcharge may be applied to the overdischarge situation aswell. The present discussion highlights the overcharge case in therepresentative discussion because it is generally associated with themore significant potential short-term risk.

The particular charge levels will vary among different cells, cellaggregations/arrangements, and cell chemistries used by ESS 100,therefore the specific shape of SOC curve 200 applicable to anyparticular ESS 100 varies. In these various implements of the presentinvention, there will be a corresponding normal range for an SOC curvewhere the operation is considered linear and end zones that are aboveand below the normal range where overcharge and overdischarge,respectively, occur resulting in the SOC curve becoming non-linear.Measuring and detecting these linear and non-linear regions by BMS 110is used to detect exceptional charge events. Once detected, BMS 110 mayassert control and/or status signals to other components for a desiredresponse.

FIG. 4 illustrates a chart of a set 400 of series element voltagesduring steady state charging. A subset of voltages are identified by aset 405 of traces that include a large number (e.g., ˜100) serieselements voltages. Battery elements 105 i of set 405 represent the bulkof battery elements that charge normally and are balanced within apredetermined threshold (e.g., +/−1%) prior to charging. The traces ofset 405 are linear in the normal range and indicate charging withindesign specification.

Set 400 includes additional traces that could represent problematicexceptional charge events. These additional traces include a first trace410 having a small (e.g., a 0.2 V offset or less) and a second trace 415having a small (e.g., 5% gain error or less) that are representative ofa 20% imbalance. Set 400 also includes traces with a larger imbalance,for example, a 30% imbalance. A third trace 420 includes a 0.3 V offsetand a fourth trace 425 includes a 7.5% gain error. For the 20%imbalance, overcharge starts at about 80% SOC while for the 30%imbalance, overcharge starts at about 70% SOC. As noted herein, both theoffset and the gain errors are broadly described as instances ofmeasurement errors. Any measurement error producing a significantdeviation of a CCV-SOC curve relative to an expected curve may beencompassed by embodiments of the present invention.

Detection

BMS 110 registers a possible series element overcharge event in responseto a sustained increase or decrease in voltage of one or more serieselements beyond some predetermined reference (the value of the referenceitself may vary). For steady state for example, the reference may be astatistically established average. For transient operation, thereference may be a value obtained from a lookup table. Thispredetermined reference may be dependent upon a total number of serieselements and/or other factors. For example this threshold may be adeviation that is more than 1.5×, 2×, or 2.5× relative to apredetermined parameter and exceeding this threshold results in thedetection of the exceptional charge event. The parameter may be astatistical assessment (e.g. a standard deviation), or some measurementor calculation or the like (e.g., an average) that is derived from adistribution (preferably a real-time distribution) of series elementvoltages during charge. For FIG. 4, overcharge is indicated by avariation in a measured value that exceeds 1% of the values of set 405.

For some embodiments, there are variations in charging behavior that areresponsive to physical conditions of ESS 100 (e.g., temperature, cyclelife, SOC, and the like that in turn are dependent on specific cell typeand chemistry). These variations can be predictable and determined inadvance to be known quite accurately. In such situations, BMS 110 mayuse a look up table for comparison of individual voltages in place ofthe evaluation of the instantaneous distribution of series elementvoltages and subsequent comparison.

The measurements, tests, and comparisons of battery element voltagesagainst the SOC curve (e.g., FIG. 2) is also pertinent to a measurement,test, and comparison of the derivation curve (e.g., FIG. 3). Forexample, BMS 110 compares first derivatives of the CCV versus SOC curvesfor battery elements 105 of ESS 100 against a predetermined reference(the predetermined value). This predetermined reference may be dependentupon a total number of series elements and/or other factors. For examplethis threshold may be a deviation that is more than 1.5×, 2×, or 2.5×relative to a predetermined parameter and exceeding this thresholdresults in the detection of the exceptional charge event. The parametermay be a statistical assessment (e.g. a standard deviation), or somemeasurement or calculation or the like) that is derived from adistribution (preferably a real-time distribution) of series elementvoltages during charge. For FIG. 4, overcharge is indicated by avariation in a measured value that exceeds 1% of the values of set 405.

Some embodiments include BMS 110 using variations of othercharacterizations of ESS 100 as a function of time. Thecharacterizations may also include elapsed time (assuming a constantcurrent charging rate), integrated charge, integrated charging energy,or estimated open-circuit voltage (OCV) that may be used in place of SOCas a dependent variable. In other embodiments, a measure of time, SOC,or integrated charge, or integrated energy, or estimated OCV versusseries element voltage could be used by BMS 110 to detect exceptionalcharge events.

While the description above includes embodiments with BMS 110 configuredfor data acquisition of individual voltages of all the battery elements,not all embodiments need be configured in this way. Some embodimentsprovide a composite assessment in which battery elements 105 arecombined into measurement units. Such a composite assessment may be inaddition to, or in lieu of, individual measurement. For example, a pairof battery elements 105 may be collectively measured and that collectivemeasurement compared against a predetermined reference. Otherembodiments may use triplets instead of pairs, or other number ofbattery elements measured together. Practically any collectiveassessment may be used provided that a precision of the measurementenables variations due to an exceptional charge event of any individualseries battery element. Such collective measurements can be comparedwith the sum of the measurements of the included individual elements,with a discrepancy indicating a possible exceptional charge event.Possible advantages of such collections include the situation thatembodiments employing such collective assessment may havecost-advantages when the collective measurement simplifies and reducesmeasurement and data acquisition components of BMS 110.

As noted elsewhere, the SOC curve includes a sharp drop in voltage atthe low SOC end of charging which BMS 110 is able to use whenidentifying possible overdischarge of a series element during dischargecycles by similar comparisons previously described. Though overdischargeis not nearly as severe an event as overcharge, detection of a potentialoverdischarge can be used to trigger an appropriate response that mayprevent possible overcharge on subsequent charging cycles.

The disclosed embodiments include several different ways of detecting anexceptional charge event associated with one or more battery elements.Embodiments of the present invention provide ESS 100 and/or BMS 110 witha range of possible responses to a detected exceptional charge event.Overcharge of one or more individual battery elements 105 duringcharging is generally viewed as the more potentially serious and urgentsituation.

As noted herein, the detection modalities are categorized based upon atype of use of ESS 100. When the use, during charging or discharging,provides for rapid changes in energy transfer to or from ESS 100, thenthe principles described in the context of transient detection areemployed. When the use, during charging or discharging, provides forsteady energy transfer that is provided at a rate fairly constant overseveral measurement cycles, then the principles described in the contextof steady state detection are employed.

A primary difference is the type of data that is collected withinmeasurement and analysis cycles. In the transient case, energy flowsrelative to ESS 100 change fairly rapidly. It may take time to gatherenough information for statistical evaluation of means, averages,deviations, and the like and in a transient operation, those values arenot as helpful to quickly and unambiguously detect an exceptional chargeevent. As a point of generality, the transient case is often associatedwith potentially larger peak energy transfer rates. Even when it may bepossible to begin to gather data over enough time, there can beincreased risk to waiting and it is desirable to employ otherfaster-responding detection modalities.

In steady state operation (e.g., charging an EV, or withdrawing currentfrom the stationary storage), the current to or from ESS 100 is regularand more predictable. When in steady state operation, the current flowrelative to ESS 100 will for the most part be constant, or at leastslowly changing, and a relatively long time history can be taken andused in the controller. This includes collecting enough data from allthe battery elements and developing the requisite reference(s), and thenperforming the tests of battery element values versus the reference(s).

In transient operation (e.g., withdrawing charge from the EV ESS orcharging the stationary storage device using wind turbines or solarpanels and the like), the current flow relative to ESS 100 will beirregular and unpredictable, and is determined by the operationalpattern (driving, wind, and sun).

In steady state operation, statistical information can determined fromlarge enough collections of data to be statistically significant. Duringoperational modes which experience predominately transient patterns,there are periods in which operation is steady enough operation toinclude steady state tests. These steady (standard deviation of absolutevoltage measurement or derivative over a period of time) can be madewhen current is relatively stable (cruising on the highway for example),but transient detection takes advantage of different characteristics ofthe cell during transient events. In particular, during a transientdischarge event such as gunning the EV for several seconds, if a severeimbalance is present that is masked by gain/offset errors, theimbalanced battery cell will deviate from the rest significantly due tomuch different cell impedance. This deviation can be detected in a fewseconds, versus the slower deviation that would occur during chargingover several minutes. A lookup table of impedance versus SOC can be usedto bound the degree of deviation that triggers a response (changes intemperature throughout the pack can also cause changes in cell impedancewhich would cause deviation in a transient current event like flooringthe car, so the controller monitors for an extreme deviation).

In this transient operation, a lookup table stores impedance values fora range of SOC values for individual battery elements (or aggregationsof battery elements). During transient operation, impedance values areestablished for each loaded battery element. The lookup table isaccessed with the loaded impedance value and produces the correspondingSOC value. If the SOC falls outside a specified range (eitherrepresenting an overcharged or overdischarged battery element) then thecontroller has detected the exceptional charge event (e.g., overchargeor overdischarge). Because changes of impedance versus SOC are notlinear, and can vary by temperature, impedance values are not comparedor used directly in the preferred embodiments. The impedance isconverted to a corresponding SOC and then the SOC is evaluated for anexceptional charge event.

Some implementations may rely on some other charge-related parameterbesides, or in addition to, impedance. When the relationship to themeasured parameter and the charge-related parameter can be calculated inreal-time without resources that are too expensive for the particularapplication, the controller may determine the numbers without referenceto a lookup table. What is too expensive is dependent upon theimplementation, with those resources including one or more ofcalculation time, parts cost, parts weight, parts reliability, and thelike.

Responses

In the disclosed embodiments, responses are based upon a type ofexceptional charge event that was detected. One set of responses relateto overcharge events and another set of responses relate tooverdischarge events.

Overcharge

Responses to a detection of a possible overcharge event (or response toa determination of a sufficient likelihood of such an event) of abattery element 105 include one or more of the following.

A simple first type of response is for BMS 110 to assert a signal thatstops any charging of ESS 100. In this way any risk of an adverse effectof overcharge may be greatly reduced.

A second type of response includes assertion by BMS 110 of a diagnostictrouble code (DTC) or malfunction indicator light (MIL). A managementsystem coupled to ESS 100 is able to detect and respond to the DTC orMIL and take further corrective action, including suspending anycharging.

A third type of response locks out future charging until ESS 100 hasbeen serviced. In some embodiments charging is not completely locked,but rather is limited to reduce overcharge risks while enabling somefunction. For an EV, the limited function is sufficient to enable the EVto be driven to a service center. Two or three of these first types ofresponse can be used together to provide a simple response modality todetected overcharge events.

A fourth type of response includes use of VMBS 125 to bleed overchargedbattery elements, or those with a significant enough chance to beovercharged, to a reduced charge level. When event detector 130 istriggered, VMBS 125 is by definition in a compromised operational modeand it therefore cannot be used to properly manage and regulate bleedingof the overcharged battery element(s). BMS 110 triggers a bleed circuit,which could be part of VMBS 125, to bleed a desired amount of chargecapacity from the subject battery elements. The amount of reduction orbleed can be implementation specific to reduce risks of overcharge to adesired level. Some embodiments bleed about 50% capacity. BMS 110 usesthe bleed circuit (e.g., a selectively engageable circuit having a knownimpedance) along with an assumed (non-measured) SOC (e.g., assume 110%SOC irrespective of measured value) to determine an amount of time tobleed energy from the subject battery element to reach the desiredreduced capacity. In some cases BMS 110 may manage the bleed and set thedesired level by monitoring bleed current directly.

A fifth type of response includes adjustment of SOC or voltage targetsbased on true SOC at the time of detection. True SOC may be determinedby BMS 110 in multiple different ways including integrated charge, totalvoltage of ESS 100, and the like. The adjustments of SOC or voltagetargets could be performed incrementally as information is collectedwith each charge cycle. In this response, the SOC target for charging isreduced by some value when the exceptional charge event is detected. Thereduction may be some set amount or be responsive to the degree ofmismatch between corresponding attributes (e.g., measured voltage) anexceptional battery element (battery element 105 having the exceptionalcharge event) and battery elements within set 405.

A sixth type of response, similar to the fifth type, reduces the max SOCor target voltage for all battery elements 105. BMS 110 causes ESS 100to run at a reduced max SOC or voltage until ESS 100 is serviced.

A seventh type of response includes use of the BMS 110 measurement anddata acquisition components to log the various events. When the detectedovercharge event is evaluated and poses no significant risk to ESS 100or operators, then logging is an appropriate response as it does notimpair operation or use which could, in some situations, pose more riskor inconvenience than the overcharge event. The logging event includesdetermination and recording of one or more of the following:temperature, SOC of all bricks, voltage measurements of all bricks,dV/dQ of all bricks at the time of the event, and charge/discharge rate.The log may be stored in BMS 110 or it may be sent to a data center forprocessing. In some embodiments, BMS 110 includes a transmitter (e.g., awireless device that uses an available network connection (such as athome or other location frequented by a mobile implementation of ESS100)) that sends the log information to a datacenter for monitoring andprocessing.

An eighth type of response includes adjustment of element parameters(e.g., voltage gain and/or voltage offset factors) for affected batteryelements 105. In this type of response to a detected exceptional chargeevent, each battery element 105 having an exceptional charging profilethat tags the battery element as experiencing a possible exceptionalcharge event is flagged. BMS 110 adjusts those element parameters toreduce the variation between the exceptional charging profile and thecharging profiles of the battery elements of set 405. Preferably theadjustments move the exceptional charging profile into set 405.

A ninth type of response addresses thermal control of ESS 100. Asdiscussed herein, some of the embodiments are implemented to addresspotential risks of a potential thermal runaway for any battery elementwith an imbalance that could, responsive to charging, lead to overchargeand excess heating. This response relates to reducing the temperature ofESS 100 and/or its components to reduce overheating which can lead tothe thermal runaway. ESS 100 typically includes some type of thermalcontrol system (e.g., a cooling system that circulates a coolant throughESS 100 to extract heat and some type of heat exchanger to transfer heatfrom the coolant and the like). This response includes BMS 110initiating increased cooling from the thermal control system. Thethermal control system is either operated at increased cooling capacityor maximum depending upon what is needed or desired to sufficientlyreduce any risk of thermal runaway. The increased cooling reduces anychance that the battery element experiencing an overcharge event has toself-heat to a point of thermal runaway.

In some embodiments, the thermal control system is engaged in theheightened cooling mode immediately upon detecting the overcharge event.As discussed above, it is also the case that the detected overchargeevent could initiate another additional response as well. Thatadditional response may correct or reduce the overcharge event, in whichcase the heightened cooling mode may be reduced or terminated. Forexample, after initiating the heightened cooling mode, the exceptionalbattery element may be bled by VMBS 125 so it is no longer overchargedand further chances of overcharging are reduced. Thereafter the thermalcontrol system may be turned off (as is typical for charging).

In other implementations, a version of this ninth type of responseincludes adjustments to one or more thermal setpoints of the thermalcontrol system. BMS 110 is able to reduce the thermal setpoints (whichinitiate actuation of the thermal control system) at a lower temperatureto provide an extra margin of safety in response to a detectedovercharge event.

A tenth type of response includes a backup response that addressessituations in which the parameter (e.g., voltage) measurement systembecomes inoperative. This backup response may, in some implementations,take a more primary role in the event a voltage measurement facilitybecomes fully inoperative (e.g. a voltage sense wire becomesdisconnected), even when there isn't an exceptional charge eventdetected. Many systems respond to an inoperative voltage measurement byimmediately disallowing drive. Some embodiments of the present operateon voltage measurements of a pair of non-contiguous battery elements,where the missing voltage measurement is of a battery element betweenthe pair of battery elements. This response allows for some protectionfrom exceptional charge events (both overcharge and overdischarge), eventhough a parameter measurement is missing for the particular batteryelement. This is a special operational mode that is not designed forsustained drive. However, including such an optional response couldallow a user to drive the car into service, rather than becomingimmediately stranded and requiring towing in the event a voltagemeasurement went dead.

Overdischarge

In the event of a detected exceptional charge event that includes anoverdischarge of one or more battery elements, BMS 110 provides one ormore appropriate responses. The following seven responses arecounterparts to some of the overcharge responses noted herein.

A first type of response to an overdischarge includes prevention offuture charging of the vehicle until the vehicle is serviced. It issomewhat counter-intuitive to address overdischarge by controlling,limiting, or preventing charging but it has been observed that someproblems which lead to overdischarge may lead to overcharge onsubsequent charging cycles.

A second type of response includes adjusting charge SOC or voltagetargets (possibly incrementally as information is collected with eachcharge cycle) based on true SOC at the time of detection. In this case,in contrast to overcharge responses, the charge SOC or voltage targetsmay be selectively increased.

A third type of response includes BMS 110 initiating ESS 100 to operateusing increased minimum SOC or voltage targets.

A fourth type of response includes logging the event, which may includeone or more of temperature, SOC of all bricks, voltage measurements ofall bricks, dV/dQ of all bricks at the time of the event, andcharge/discharge rate. As noted above, the log may be stored in aninternal memory associated with ESS 100 or communicated to a datacenter. The internal memory does not have to physically be part of ESS100 but may be included in another control or data acquisition systemelectrically communicated with ESS 100.

A fifth type of response includes adjustments to parameters (e.g.,gain/offset factor) for the affected battery element. In some cases theadjustment may also affect other battery elements in addition to thetargeted battery elements. That is, some parameter adjustments mayaffect several elements and BMS 110 may need to use a secondaryadjustment modality to compensate for having adjusted non-targetedbattery elements.

A sixth type of response includes a backup response that addressessituations in which the parameter (e.g., voltage) measurement systembecomes inoperative. This backup response may, in some implementations,take a more primary role in the event a voltage measurement facilitybecomes fully inoperative (e.g. a voltage sense wire becomesdisconnected), even when there isn't an exceptional charge eventdetected. Many systems respond to an inoperative voltage measurement byimmediately disallowing drive. Some embodiments of the present operateon voltage measurements of a pair of non-contiguous battery elements,where the missing voltage measurement is of a battery element betweenthe pair of battery elements. This response allows for some protectionfrom exceptional charge events (both overcharge and overdischarge), eventhough a parameter measurement is missing for the particular batteryelement. This is a special operational mode that is not designed forsustained drive. However, including such an optional response couldallow a user to drive the car into service, rather than becomingimmediately stranded and requiring towing in the event a voltagemeasurement went dead.

A seventh type of response includes BMS 110 limiting a maximum currentdraw from ESS 100. This response artificially throttles back the poweravailable to the EV which prevents rapid discharging and possibleoverheating during the exceptional charge event. This response isn'tgenerally applicable to overcharge because the charging current would beset by the charging parameters and the currents are generally much lowerthan during discharge.

FIG. 5 illustrates a system 500 implementing exceptional charge eventdetection and response. System 500 includes an energy environment 505that encompasses ESS 100, a control system 510, an energy converter 515,and a support system. Energy environment 505 may be an electric vehicleor other context in which electrical energy is stored and converted.Control system 510 monitors state and status of the various componentsand includes I/O (input/output) features appropriate to the context,such as receiving input from a user regarding velocity. Control system510 typically includes a stored program computing system that has memoryand a processing unit configured to implement control mechanisms of thecomponents of system 500. Control system 510 may be integrated wholly orpartially with another component of system 500, such as with BMS 110 ofESS 100. In other cases, some or all of the functions of BMS 110 may beimplemented by control system 510. Energy converter 515 represents oneor more elements that use energy from ESS 100. These elements mayinclude electric motors (e.g., an electric propulsion motor) and otherdevices that use energy in energy environment 505. Support 520represents thermal control systems and other components of energyenvironment 505 that support its use and operation.

System 500 further includes a charger 525 that is typically a stationaryenergy charging station and provides a source of power (typically ACpower) that is used to charge the battery elements of ESS 100. One ormore components of energy environment 505 may implement any of thedetection and response modalities describe herein.

FIG. 6 illustrates a flowchart for a detection process 600. Process 600includes steps 605-630 to establish an existence, or likelihood ofexistence, of an exception charge event (ECE). Step 605 first assessesthe reference. In a simple case, ESS 100 includes monitoring and dataacquisition equipment (e.g., voltage and current sensors and logicdevices for measurement and evaluation) of the reference that will beused. During charging, the ECE of most concern is the overcharge event,while overdischarge could be relevant during charging of ESS 100 as wellas during operation of energy environment 505.

The reference of step 605 is preferably a statistical representation ofsamples of the collection of voltages of battery elements 105 of ESS100. Other references may be employed, such as outputs of look-up tablesor other data organization.

Next in process 600 after step 605, step 610 determines desiredparameter values for individual battery elements 105. The discussionincludes several ways to do this, including measuring individual voltagelevels or measuring voltage levels of aggregations (e.g., pairs ofbattery elements 105).

Next step 615 performs a comparison of the determined individual voltagelevels against the reference. In a preferred embodiment, a determinationof a charge event as normal or exceptional is based upon an evaluationof parameter value performance, which in turn can be dependent upontransient or steady state operation. Specifically for steady stateoperation, upon the SOC curve and the derivation curve. In this sense,this type of detection implemented by the embodiments of the presentinvention are not instantaneous determinations as this process isresponsive to trend of the parameter values of the battery elements,preferably as a function of state of charge, and most preferably asloaded battery element voltage as a function of SOC. Transientoperation, as noted above, is more instantaneous and can provide quickerresponses.

After, or during, the comparison of parameter values against thereference, process 600 at step 620 tests the results of the comparisonagainst a threshold value. Depending upon how the test is implemented(e.g., whether exceeding a threshold is true or not exceeding thethreshold is true), step 620 establishes whether a particular comparisonrepresents, or has a sufficient likelihood to represent, an exceptionalcharge event. Further differentiation is based upon whether system 500is charging at the time of the test. Exceptional charge events duringcharging typically represent overcharge events and exceptional chargeevents at other times typically represent overdischarge events.

When process 600 does not determine that an ECE exists at the test ofstep 620, process 600 continues with the detection process. What thatmeans is dependent upon specifics of how steps 605-620 were implemented.For an interrupt-driven test, step 625 returns to the operation it wasperforming when interrupted. In some cases step 615 and step 620 arecombined, so step 625 returns to step 615 for another comparison ofanother parameter against the reference. In some cases process 600updates the reference so step 625 returns to step 605 to determinewhether the reference needs to be updated. Step 625 can simply return tostep 610 to continue to monitor parameters of battery elements 105.

When the test at step 620 is true, process 600 uses the comparison toidentify and flag the exceptional battery element as having anexceptional charge event (which may be further identified as anovercharge or an overdischarge charge event based uponuse/implementation and a status of charging from charger 525. Mostimplementations further include one or more responses to any detectedECE at step 630. The response may be dependent upon the type of ECE aswell. Embodiments of the present invention described herein includerepresentative types of responses.

FIG. 7 illustrates a graph of a transient discharge event 700 for a setof series battery elements; and FIG. 8 illustrates a graph of atransient charge event 800 for a set of series battery elements. Event700 and event 800 make use of impedance for transient detection ofexceptional charge events. In each graph, the set of curves that aregenerally matched represent series elements that are not exceptionallycharged. A series element 705 in the transient discharge event 700 and aseries element 805 in the transient charge event represent exceptionallycharged elements. Outside of the transient event, each exceptionalcharge element appears like a non-exceptionally charged element becauseof measurement offset/gain error during no/low current draw. During ahigh current draw, such as event 700, the voltage of all series elementsdrop as current is pulled from the elements (discharge), but theexceptionally charged element drops significantly more than the rest(FIG. 7). During a high current charge, such as event 800, the voltageof all series elements rise as current is transferred to the elements(charge), but the exceptionally charged element rises significantly morethan the rest (FIG. 8). The detection methods outlined would detectthese exceptional charge events. The impedance approach is usefulbecause the very high current pulse magnifies the effects of theimpedance difference. During a steady state event, currents aretypically much (˜10×) lower, so the impedance approach wouldn't be asuseful as the steady observation of voltage drift with time.

The system and methods above has been described in general terms as anaid to understanding details of preferred embodiments of the presentinvention. In the description herein, numerous specific details areprovided, such as examples of components and/or methods, to provide athorough understanding of embodiments of the present invention. Somefeatures and benefits of the present invention are realized in suchmodes and are not required in every case. One skilled in the relevantart will recognize, however, that an embodiment of the invention can bepracticed without one or more of the specific details, or with otherapparatus, systems, assemblies, methods, components, materials, parts,and/or the like. In other instances, well-known structures, materials,or operations are not specifically shown or described in detail to avoidobscuring aspects of embodiments of the present invention.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

Additionally, any signal arrows in the drawings/Figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted. Furthermore, the term “or” as used herein isgenerally intended to mean “and/or” unless otherwise indicated.Combinations of components or steps will also be considered as beingnoted, where terminology is foreseen as rendering the ability toseparate or combine is unclear.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims. Thus, the scope of the invention is to bedetermined solely by the appended claims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A microprocessor-implemented response systemfor an exceptional charge event in an energy storage system having aplurality of series-connected battery elements, comprising: a firstcharge imbalance detection system monitoring, using the microprocessor,the energy storage system for a charge imbalance using a first detectionmodality, said first charge imbalance detection system initiating areduction of said charge imbalance using a first response modality; asecond charge imbalance detection system monitoring, using themicroprocessor, the energy storage system for an exceptional chargeevent of a particular one battery element of the plurality of batteryelements using a second detection modality different from said firstdetection modality, wherein said exceptional charge event includes anovercharge of a battery element during a charging event, wherein saidfirst detection modality includes a measurement of a voltage level ofeach battery element of the plurality of battery elements establishing aplurality of voltage imbalances between individual ones of the pluralityof battery elements, wherein said first response modality includesadjusting said voltage levels to reduce said plurality of voltageimbalances, and wherein said second detection modality includes astatistical evaluation of a parameter of each battery element; and aremediation system initiating a response to said exceptional chargeevent using a second response modality different from said firstresponse modality, said response decreasing a risk associated with saidexceptional charge event, wherein said exceptional charge event isassociated with a particular one battery element having a particularcharge target and wherein said response includes a reduction of saidparticular charge target.
 2. The microprocessor-implemented responsesystem of claim 1 wherein said response further includes a suspension ofsaid charging event.
 3. The microprocessor-implemented response systemof claim 1 wherein said response further includes setting a serviceflag.
 4. The microprocessor-implemented response system of claim 1wherein said response further includes activating a visual indicator. 5.The microprocessor-implemented response system of claim 1 wherein saidresponse further includes inhibiting any charging event until the energystorage system is serviced.
 6. A microprocessor-implemented responsesystem for an exceptional charge event in an energy storage systemhaving a plurality of series-connected battery elements, comprising: afirst charge imbalance detection system monitoring, using themicroprocessor, the energy storage system for a charge imbalance using afirst detection modality, said first charge imbalance detection systeminitiating a reduction of said charge imbalance using a first responsemodality; a second charge imbalance detection system monitoring, usingthe microprocessor, the energy storage system for an exceptional chargeevent of a particular one battery element of the plurality of batteryelements using a second detection modality different from said firstdetection modality, wherein said exceptional charge event includes anovercharge of a battery element during a charging event, wherein saidfirst detection modality includes a measurement of a voltage level ofeach battery element of the plurality of battery elements establishing aplurality of voltage imbalances between individual ones of the pluralityof battery elements, wherein said first response modality includesadjusting said voltage levels to reduce said plurality of voltageimbalances, and wherein said second detection modality includes astatistical evaluation of a parameter of each battery element; and aremediation system initiating a response to said exceptional chargeevent using a second response modality different from said firstresponse modality, said response decreasing a risk associated with saidexceptional charge event, wherein said exceptional charge event isassociated with a particular one battery element having a particularcharge storage capacity and wherein said response includes use of saidfirst response modality to reduce a stored charge of said particular onebattery element to a predetermined fraction of said particular chargestorage capacity intentionally creating an imbalance.
 7. Themicroprocessor-implemented response system of claim 6 whereinpredetermined fraction is in the range of 50%+/−10%.
 8. Themicroprocessor-implemented response system of claim 1 wherein saidexceptional charge event is associated with a particular one batteryelement having a particular charge storage capacity and wherein saidresponse includes use of a response modality similar in operation tosaid first response modality to directly reduce a stored charge of saidparticular one battery element responsive to an assumed stored chargeand a predetermined impedance electrically communicated to saidparticular one battery element for a time calculated to reduce saidassumed stored charge to a predetermined fraction of said particularcharge storage capacity.
 9. The microprocessor-implemented responsesystem of claim 8 wherein predetermined fraction is in the range of50%+/−10%.
 10. The microprocessor-implemented response system of claim 1wherein said charging event includes an associated maximum charge targetand wherein said response further includes a reduction of saidassociated maximum charge target.
 11. The microprocessor-implementedresponse system of claim 1 wherein said response further includeslogging a set of data associated with said exceptional charge event. 12.A microprocessor-implemented response system for an exceptional chargeevent in an energy storage system having a plurality of series-connectedbattery elements, comprising: a first charge imbalance detection systemmonitoring, using the microprocessor, the energy storage system for acharge imbalance using a first detection modality, said first chargeimbalance detection system initiating a reduction of said chargeimbalance using a first response modality; a second charge imbalancedetection system monitoring, using the microprocessor, the energystorage system for an exceptional charge event of a particular onebattery element of the plurality of battery elements using a seconddetection modality different from said first detection modality, whereinsaid exceptional charge event includes an overcharge of a batteryelement during a charging event, wherein said first detection modalityincludes a measurement of a voltage level of each battery element of theplurality of battery elements establishing a plurality of voltageimbalances between individual ones of the plurality of battery elements,wherein said first response modality includes adjusting said voltagelevels to reduce said plurality of voltage imbalances, and wherein saidsecond detection modality includes a statistical evaluation of aparameter of each battery element; and a remediation system initiating aresponse to said exceptional charge event using a second responsemodality different from said first response modality, said responsedecreasing a risk associated with said exceptional charge event, whereinthe energy storage system includes a thermal control system providing atemperature control of the plurality of battery elements responsive to athermal profile and wherein said response includes a modification tosaid thermal profile actuating said thermal control system at anincreased cooling capacity.
 13. The microprocessor-implemented responsesystem of claim 1 wherein said particular one battery element has anassociated gain factor used when charging said particular one batteryelement and wherein said response further includes a reduction to saidassociated gain factor.
 14. The microprocessor-implemented responsesystem of claim 1 wherein said particular one battery element has anassociated voltage offset factor used when charging said particular onebattery element and wherein said response further includes a reductionto said associated voltage offset factor.
 15. A computer-implementedmethod to respond to an exceptional charge event in an energy storagesystem having a plurality of series-connected battery elements,comprising: monitoring, using the microprocessor, the energy storagesystem for a charge imbalance using a first detection modality; reducingsaid charge imbalance using a first response modality; monitoring, usingthe microprocessor, the energy storage system for an exceptional chargeevent of a particular one battery element of the plurality of batteryelements using a second detection modality different from said firstdetection modality, wherein said exceptional charge event is anovercharge of said particular one battery element; and decreasing a riskassociated with said exceptional charge event using a second responsemodality different from said first response modality, wherein saiddecreasing-risk step includes bleeding energy from said particular onebattery element.
 16. The method of claim 15 further comprisingtransferring energy to the plurality of series-connected batteryelements from a charging station and wherein said decreasing-risk stepfurther includes asserting a stop charging signal to said chargingstation and suspending said energy transferring.
 17. The method of claim16 further comprising setting an overcharge status flag whenever saidovercharge is detected and wherein said stop charging signal remainsasserted as long as said overcharge status flag remains set.
 18. Themethod of claim 15 further comprising transferring energy to theplurality of series-connected battery elements from a charging stationand wherein said decreasing-risk step further includes asserting areduced charging signal to said charging station and limiting saidenergy transferring to prevent charging to 100% SOC.
 19. The method ofclaim 18 further comprising setting an overcharge status flag wheneversaid overcharge is detected and wherein said reduced charging signalremains asserted as long as said overcharge status flag remains set. 20.The method of claim 15 wherein said decreasing-risk step furtherincludes asserting a diagnostic trouble code when detecting saidovercharge.
 21. The method of claim 15 wherein said decreasing-risk stepfurther includes providing a visual indication of said overcharge. 22.The method of claim 15 wherein said energy bleeding is not performed bysaid first response modality and includes assuming an SOC for saidparticular one battery element and selectively coupling a predeterminedimpedance to said particular one battery element to discharge energyfrom said particular one battery element at a rate responsive to saidSOC until a calculated SOC responsive to said SOC and to saidpredetermined impedance reaches a predetermined SOC level.
 23. Themethod of claim 15 wherein said particular one battery element includesan SOC charge target wherein said decreasing-risk step includes reducingsaid SOC charge target.
 24. The method of claim 15 wherein the pluralityof battery elements each includes an SOC charge target wherein saiddecreasing-risk step includes reducing said SOC charge target.
 25. Acomputer-implemented method to respond to an exceptional charge event inan energy storage system having a plurality of series-connected batteryelements, comprising: monitoring, using the microprocessor, the energystorage system for a charge imbalance using a first detection modality;reducing said charge imbalance using a first response modality;monitoring, using the microprocessor, the energy storage system for anexceptional charge event of a particular one battery element of theplurality of battery elements using a second detection modalitydifferent from said first detection modality, wherein said exceptionalcharge event is an overcharge of said particular one battery element;and decreasing a risk associated with said exceptional charge eventusing a second response modality different from said first responsemodality, wherein said particular one battery element includes anadjustment profile including one or more of voltage gain and voltageoffset factors and wherein said decreasing-risk step includes adjustingsaid adjustment profile.
 26. A computer-implemented method to respond toan exceptional charge event in an energy storage system having aplurality of series-connected battery elements, comprising: monitoring,using the microprocessor, the energy storage system for a chargeimbalance using a first detection modality; reducing said chargeimbalance using a first response modality; monitoring, using themicroprocessor, the energy storage system for an exceptional chargeevent of a particular one battery element of the plurality of batteryelements using a second detection modality different from said firstdetection modality, wherein said exceptional charge event is anovercharge of said particular one battery element; and decreasing a riskassociated with said exceptional charge event using a second responsemodality different from said first response modality, wherein theplurality of battery elements each includes an adjustment profileincluding one or more of voltage gain and voltage offset factors andwherein said decreasing-risk step includes adjusting said adjustmentprofiles.
 27. The method of claim 15 further comprising transferringcoolant to the plurality of series-connected battery elements from acoolant system to effect a cooling operation of the plurality ofseries-connected battery elements and wherein said decreasing-risk stepincludes increasing said cooling operation to reduce a temperature ofsaid particular one battery element.
 28. The method of claim 15 furthercomprising transferring coolant to the plurality of series-connectedbattery elements from a coolant system to effect a cooling operation ofthe plurality of series-connected battery elements using a set ofpredetermined thermal setpoints and wherein said decreasing-risk stepincludes lowering one or more setpoints of said set of predeterminedthermal setpoints to increase said cooling operation.
 29. Themicroprocessor-implemented response system of claim 6, wherein saidresponse further includes inhibiting any charging event until the energystorage system is serviced.
 30. The microprocessor-implemented responsesystem of claim 12, wherein said charging event includes an associatedmaximum charge target and wherein said response further includes areduction of said associated maximum charge target.
 31. The method ofclaim 25, further comprising transferring coolant to the plurality ofseries-connected battery elements from a coolant system to effect acooling operation of the plurality of series-connected battery elementsand wherein said decreasing-risk step includes increasing said coolingoperation to reduce a temperature of said particular one batteryelement.
 32. The method of claim 26, further comprising transferringcoolant to the plurality of series-connected battery elements from acoolant system to effect a cooling operation of the plurality ofseries-connected battery elements using a set of predetermined thermalsetpoints and wherein said decreasing-risk step includes lowering one ormore setpoints of said set of predetermined thermal setpoints toincrease said cooling operation.